7 Common Gardening Myths Debunked

27 November 2014, written by Benedict Vanheems

Gardeners are a generous lot, freely sharing top tips and know-how to help out their fellow green-fingered enthusiasts – but while advice is dispensed with the best of intentions it can sometimes be misleading. We investigate some popular gardening myths - and promptly debunk them, saving you time, effort and disappointment.

Myth 1: Compost bins must sit on soil

Worms and micro-organisms in the soil need to have contact with the compost ingredients in order to kick-start decomposition, but while composting directly on grass or soil certainly speeds up the process, it’s not essential – compost bins work just as well on a hard surface such as concrete or paving slabs.

You can prime a new compost bin by adding some mature compost from another bin. Or add garden soil along with the first batch of ingredients to introduce all those beneficial soil organisms. Worms will successfully make their way into a compost bin sitting on a hard surface. A thick layer of cardboard or newspaper at the base of the bin will help to attract them.

Myth 2: Always stake young trees

Not all trees need to be staked when they are planted. Very young trees left to sway in the wind will develop a thicker trunk, sturdier branches and a more supportive root system. While grafted trees and trees older than two years will appreciate some initial support, stakes and ties should be removed as soon as possible to prevent over-reliance, which can lead to a weaker tree. It may seem counterintuitive, but you’ll nurture a stronger tree. The one exception is the very smallest grafted apple trees which always need support – check with your supplier if you are planting these.

Myth 3: Stones in pots improve drainage

How many times have you added stones, gravel or ‘crocks’ of broken terracotta pots into the bottom of containers to improve drainage? You can ensure adequate drainage instead by using good-quality potting soil and by selecting containers with plenty of drainage holes in the base, or adding your own. Stand containers on pot feet or pebbles so that excess water can freely drain out from the drainage holes. As an added bonus pot feet also make life harder for slugs.

Myth 4: Eggshells discourage slugs

We are often told that crushed egg shells create an impenetrable barrier to slugs. This may be true if they are laid thickly enough, but consider how many eggs you’d need to eat to protect any more than a couple of plants!

Slugs congregate under dark, damp places, so lay planks of wood, stone slabs or upturned grapefruit shells in strategic locations then patrol regularly to collect and destroy them. Or sink small pots filled with beer into the ground – slugs love beer and will drown trying to drink it. You can also raise plants above the ground in wall-mounted containers, or protect crops in pots with copper bands or a barrier of petroleum jelly.

Myth 5: Plant potatoes on Good Friday

An obvious myth because the date for Good Friday varies from year to year, falling anywhere between the 22nd March and the 25th of April. Then of course there’s the climate, which varies dramatically depending on where in the world you grow, and your garden’s own unique microclimate.

Our Garden Planner’s Plant List calculates the best range of planting dates for where you are, based on accurate frost data for your area sourced from our database of thousands of weather stations.

Myth 6: Pea and bean roots feed the soil

Peas and beans are members of the legume family. Legumes use soil bacteria to fix nitrogen from the air onto their roots. Logic follows that you should leave the roots of old peas and beans in the soil to feed the next crop, especially nitrogen-hungry vegetables such as cabbage. However your peas or beans will have used almost all the nitrogen up themselves. Most of the nitrogen collects in the picked pods, leaving very little in the soil. To get the most from any nitrogen in the plants the whole plant should instead be added the compost heap or dug into the ground before they flower and begin to draw on the nitrogen fixed at their roots.

Myth 7: Organic pesticides are harmless

Just because a pesticide is organic in origin, doesn’t mean it’s necessarily harmless. Just like chemical pesticides, many organic substitutes won’t discriminate between pests and the beneficial insects eating the pests.

Take the insect killer pyrethrum as an example. While it kills aphids, whiteflies and hungry caterpillars, it also wipes out good insects such as ladybirds and lacewings that would have naturally controlled them. Instead of spraying, work with nature and draw these beneficial bugs to your plot by building an insect hotel or growing plants that attract them.